Michael Freund is Founder and Chairman of Shavei Israel (www.shavei.org), which reaches out and assists "lost Jews" seeking to return to the Jewish people. He writes a syndicated column and feature stories for the Jerusalem Post. Previously, he served as Deputy Director of Communications & Policy Planning in the Israeli Prime Minister´s Office under former premier Benjamin Netanyahu.

Turkish Prime Minister Recep Tayyip Erdogan has done it again. Despite his extensive efforts to masquerade as an enlightened and civilized statesman, his temper got the best of him last week, peeling away the veil to reveal for all to see his profound hatred of Israel and the Jewish people.

Speaking at the Fifth Alliance of Civilizations Forum in Vienna's Hofburg Palace, in the very same country where Hitler was born, the Turkish leader declared Zionism to be a "crime against humanity" and equated it with anti- Semitism, fascism and Islamophobia. This from a man whose country continues to deny its own acts of genocide against the Armenian people a century ago, and its brazen oppression of its Kurdish minority today.

Needless to say, this is hardly the first time Erdogan has shown his true colors. On more than one occasion in recent years, he has hurled venom and vitriol at the Jewish state. Just four months ago, on November 19, at a conference of the Eurasian Islamic Council in Istanbul, Erdogan accused Israel of carrying out the "mass killing of Muslims" and massacring children in Gaza.

"For this reason," he explained, "I say that Israel is a terrorist state and its acts are terrorist acts." And who can possibly forget his dramatic performance at the World Economic Forum in Davos four years ago? On January 29, 2009, Erdogan shared the stage with President Shimon Peres, and the two clashed over the IDF's counterterrorism operation in Gaza aimed at halting Palestinian rocket attacks. At a certain point in the discussion, the Turkish prime minister became incensed and got up from his seat. He was, the New York Times reported, "red-faced, and with one hand grasping the arm of the moderator." Erdogan then turned to Peres, one of Israel's biggest political doves, and said to him, "Your voice comes out in a very loud tone and the loudness of your voice has to do with a guilty conscience.

When it comes to killing, you know well how to kill," before storming out of the room.

And how about the Mavi Marmara affair, when Turkey facilitated the attempt to break Israel's blockade of Gaza? ERDOGAN'S RHETORIC and behavior is more befitting of a neighborhood thug than a regional power with diplomatic ambitions. As a member of NATO and a would-be EU candidate, Turkey clearly needs to be taught a lesson by the West, which cannot and must not tolerate such disgraceful behavior. Erdogan's radicalism and rancor only contribute to the further destabilization of the region, and undermine any chances of bringing about peace and understanding.

There are various political, economic and diplomatic levers that the US and European countries can use to bring about a change in Erdogan's conduct. But don't hold your breath waiting for that to happen. If the virtual apathy which greeted Erdogan's eruption last week is any indication, Israel and its supporters should be very worried.

Take, for example, US Secretary of State John Kerry, who happened to be visiting Turkey the day after Erdogan's outburst. Speaking at a news conference with Turkish Foreign Minister Ahmet Davutoglu at his side, Kerry offered a mealy-mouthed denunciation, saying that, "We not only disagree with it, we found it objectionable."

Objectionable? When you are served the wrong soup in a restaurant, that would be considered objectionable.

But when someone says that the ideological underpinning of your nation's closest ally in the Middle East is akin to fascism, it is far more than merely objectionable.

It is loathsome and repugnant, Mr. Secretary.

Similarly, UN Secretary-General Ban Ki-moon, who was present during Erdogan's speech, waited nearly 24 hours before dispatching his spokesman to mumble a few words of disagreement to the press regarding Erdogan's characterization of Zionism.

This cannot be allowed to stand. Hence, Israel should consider withdrawing its ambassador from Ankara, downgrading relations with Turkey and cutting back on Israeli tourism and investment, until Erdogan apologizes for his slur. We need to make it clear that any assault on Zionism is an attack on the very conceptual foundation of the Jewish state and its right to exist.

After all, Zionism is the national liberation movement of the Jewish people, the set of ideas that give expression to our age-old hope of regaining sovereignty in the land of our ancestors. If someone opposes Zionism, it means they aim to deny freedom and self-determination to the Jewish people, which is akin to anti-Semitism. And that, Mr. Erdogan needs to learn, is the real "crime against humanity" which will not be tolerated.